The present invention relates to dental implant systems.
There are many dental implant systems being marketed today by different manufacturers. The components of these systems are typically incompatible with one another meaning that a xe2x80x9cmix-and-matchxe2x80x9d dental prosthesis is not possible. Clearly there would be many advantages to having the facility to build a dental prosthesis from components of different systems. For example, some systems include components which no other system has an equivalent to, that is to say they are unique, while some systems may have components with advantageous properties compared to the equivalent components of other systems.
The most widespread dental implant system at the present time is that marketed by Nobelpharma AB and known as the Brxc3xa5nemark System(copyright). This system includes a fixture as a component part thereof which is adapted in use to be embedded in the bone tissue of the maxilla or mandible and which presents at the trailing end thereof a male hexagonal projection in which an internally threaded bore opens centrally. A variety of other components of the Brxc3xa5nemark System(copyright) are then added temporarily or permanently to the trailing end of the fixture Component to form a dental prosthesis.
For example, the Brxc3xa5nemark System(copyright) includes various transmucosal spacers or abutments as component parts for connection to an implanted fixture to bridge the soft tissue layer or gingiva overlying the maxilla or mandible and carry supragingival components of the Brxc3xa5nemark System(copyright). One such abutment includes a sleeve part one of the open ends of which has an inner circumference of hexagonal cross-section for anti-rotational connection of the abutment sleeve to the trailing end of the fixture. An abutment screw then passes through the abutment sleeve to screw into the internally threaded bore in the trailing end of the fixture to secure the abutment sleeve to the fixture.
The trailing end of the abutment presents a profile such that supragingival components of the Brxc3xa5nemark System(copyright) can be added temporarily or permanently on the fixture-abutment assembly to complete the formation of a dental prosthesis. For example, in the case of the abutment assembly described hereinabove an internally threaded bore may open in the trailing end of the abutment screw for either a screw threaded projection on a supragingival component to screw into to secure that component to the fixture-abutment assembly or a screw part of a multi-part supragingival assembly to screw into to secure the supragingival assembly to the fixture-abutment assembly.
Abutments may also present anti-rotational surfaces for co-operation with anti-rotational surfaces on the leading end of supragingival components or assemblies for anti-rotational connection of the supragingival components or assemblies to the fixture-abutment assembly or wrench engaging surfaces which enable tightening of the abutment to the fixture but which do not interfere with the connection of the supragingival components or assemblies to the fixture-abutment assembly.
As examples of supragingival components there may be mentioned cylinders which carry a restoration such as a bridge or crown and impression copings which are temporarily connected to the implanted fixture-abutment assembly to enable a model of the implanted fixture-abutment assembly and surrounding dentition to be generated for fabrication of a restoration on a cylinder which will fit in with the surrounding dentition when carried by the fixture-abutment assembly.
In addition to the dental implant systems such as the Brxc3xa5nemark System(copyright) which are based on fixtures having male projections at the trailing ends thereof there also exist dental implant systems which rely on a conical seat interface between the fixtures and superstructures carried thereby. In these systems a frusto-conical recess opens in the trailing end of the fixture for a complementary frusto-conical profile at the leading end of the superstructure, for example an abutment, to seat in. The frusto-conical recess typically forms the trailing portion of a socket which at the leading end thereof defines an internally threaded bore. The superstructure is secured to the fixture through a screw connection in the internally threaded bore.
One such system is marketed by Astra Tech AB information about which can be found in inter alia xe2x80x98Dental Implants: A Guide for the General Practitionerxe2x80x99. Michael Norton, Ouintessence Publishing Co. Ltd., 1995. To prevent rotation of an abutment of this system of the type comprising an abutment sleeve and abutment screw, the socket in the fixture may further comprise a polygonal cross-section portion between the frusto-conical and internally threaded portions with the abutment sleeve being provided with a projection at the leading end thereof having a trailing frusto-conical portion for seating in the frusto-conical portion of the fixture socket and a leading polygonal portion for co-operation with the polygonal portion of the fixture socket. The abutment screw passes through the sleeve into engagement with the internally threaded bore to secure the sleeve to the fixture as for the corresponding abutment of the Brxc3xa5nemark System(copyright).
Tests have shown that a tapered seat interface such as the conical seat interface for a fixture-superstructure assembly, for example a fixture-abutment assembly, leads to an implanted assembly which exhibits greater mechanical stability and strength as compared to the fixtures of the other systems discussed hereinabove.
In addition, the fixture of the Astra Tech system has a unique outer surface characteristic which improves the shear strength of the fixture when implanted and also the ability of the fixture to osseointegrate into the bone tissue of tho maxilla or mandible into which it is implanted.
There is thus a need for the provision of means to enable a fixture of a first dental implant system having a trailing end in which a tapered, for example frusto-conical, recess is provided to support components of a second incompatible dental implant system for the formation of a hybrid dental prosthesis founded on the fixture with the recess.
With this need in mind, the present invention provides a dental implant system converter structure for enabling a fixture of a first dental implant system having a trailing end in which a tapered recess opens to support components of a second incompatible dental implant system, the converter structure having a leading end which presents a projection having a tapered profile for seating in the tapered recess in the trailing end of the fixture and a trailing end which presents a profile adapted to enable one or more components of the second dental implant system to be carried thereon.
In an embodiment of the invention he tapered recess forms a trailing portion of a socket in the trailing end of the fixture with a leading portion of the socket presenting an internally threaded bore and the tapered profile forms a trailing portion of the projection at the leading end of the converter structure with a leading portion of the projection presenting a screw threaded profile for screw connection in the internally threaded bore portion of the fixture socket.
In an embodiment of the invention the converter structure comprises a sleeve element having a leading end which presents a first part of the projection which comprises the tapered profile and a screw element having a leading end which presents a second part of the projection which comprises the screw thread profile, the screw element adapted to be inserted into the sleeve element for the screw thread profile to be screwed in the internally threaded bore portion of the fixture socket to secure the sleeve element to the fixture. The, converter structure may, on the other hand, be a one-piece component with the projection being formed at the leading end of the component.
In an embodiment of the invention the converter structure comprises anti-rotation means for co-operation with anti-rotation means on the fixture when the tapered profile of the converter structure seats in the tapered recess in the fixture to prevent rotation of the converter structure about the axis thereof relative to the fixture. For example, the anti-rotation means may be the faces of a polygonal profile such as a hexagon presented by the projection for co-operation with the faces of a polygonal cross-section portion in the fixture socket.
When the projection is formed in part on a sleeve element and in part by a screw element as outlined hereinabove, it is convenient for the polygonal profile to be formed as a leading portion of the first part of the projection on the sleeve element with the tapered profile forming a trailing portion of the first part of the projection and the polygonal cross-section portion to be formed in the fixture socket on the leading side of the tapered recess portion, for example between the internally threaded bore portion and the tapered recess portion.
In an embodiment of the invention the converter structure is adapted to convert the trailing end presented by the fixture of the first dental implant system into the trailing end of a fixture of the second dental implant system. This has the advantage that the dental prosthesis can include the abutment of the second dental implant system as well as the supragingival components thereof when the fixture of the first system is one whose trailing end does not bridge the soft tissue layer overlying the maxilla or mandible when implanted. As an example, the trailing end presented by the converter structure may correspond to the trailing end of a fixture of the Brxc3xa5nemark System(copyright).
In an alternative embodiment of the invention the converter structure takes the form of an abutment structure having a trailing end profile which allows supragingival components of the second dental implant system to be carried thereon. As an example, the sleeve element of the converter structure may be in the form of an abutment sleeve and the screw element in the form of an abutment screw.
In an embodiment of the invention the trailing end of the converter structure presents an anti-rotation profile for co-operation with a complementary anti-rotation profile presented by the leading end of a component of the second dental implant system. For example, where the fixture of the first system is one whose trailing end does not bridge the soft tissue layer overlying the maxilla or mandible when implanted and the converter structure is such as to convert the fixture of the first dental implant system to a corresponding fixture of the second dental implant system, the anti-rotation profile presented by the trailing end of the converter structure may be a male polygonal projection for anti-rotational interfacial engagement with a complementary female polygonal socket in the leading end of an abutment of the second dental implant system.
In a preferred embodiment of the invention the tapered recess which opens in the trailing end of the fixture and the tapered profile presented by the converter structure are respectively a frusto-conical recess and a complementary frusto-conical profile.
According to the invention there is further provided a dental prosthesis including a dental implant system converter structure in accordance with the invention.
According to the invention there is yet further provided a dental implant system including a dental implant system converter structure according to the invention.
According to the invention there is additionally provided the use of a dental implant system converter structure in accordance with the invention in the formation of a hybrid dental prosthesis comprising the fixture of the first dental implant system and a superstructure from the second dental implant system.
According to the invention there is also provided a method of treating toothlessness in a maxilla or mandible of a patient comprising the steps of implanting in the maxilla or mandible a fixture of a first dental implant system, mounting on the fixture a dental implant system converter structure according to the invention and mounting on the converter structure a superstructure formed from one or more components of a second incompatible dental implant system which supports or presents one or more artificial teeth.